This invention relates to high temperature electrochemical converters, such as fuel cells, and more specifically to high performance energy, or power, systems that employ electrochemical converters.
Electrochemical converters, such as fuel cells, convert chemical energy derived from fuel stocks directly into electrical energy. One type of fuel cell includes a series of electrolyte units, onto which fuel and oxidizer electrodes are attached, and a similar series of interconnectors disposed between the electrolyte units to provide electrical connections. Electricity is generated through electrodes and the electrolyte by an electrochemical reaction that is triggered when a fuel, e.g., hydrogen, is introduced over the fuel electrode and an oxidant, e.g., air, is introduced over the oxidizer electrode. Alternatively, the electrochemical converter can be operated in an electrolyzer mode, in which the electrochemical converter consumes electricity and input reactants and produces fuel.
When an electrochemical converter, such as a fuel cell, performs fuel-to-electricity conversion in a fuel cell mode, waste energy is generated and should be properly processed to maintain the proper operating temperature of the electrochemical converter and to boost the overall efficiency of the power system. Conversely, when the converter performs electricity-to fuel conversion in the electrolyzer mode, the electrolyte must be provided with heat to maintain its reaction. Furthermore, the fuel reformation process, often used with fuel cells, can require the introduction of thermal energy. Thus thermal management of the electrochemical converter system for proper operation and efficiency is important.
Thermal management techniques can include the combination of an electrochemical converter with other energy devices in an effort to extract energy from the waste heat of the converter exhaust. For example, U.S. Pat. No. 5,462,817, issued to Hsu describes certain combinations of electrochemical converters and bottoming devices that extract energy from the converter for use by the bottoming device.
Environmental and political concerns associated with traditional combustion-based energy systems, such as coal or oil fired electrical generation plants, are boosting interest in alternative energy systems, such as energy systems employing electrochemical converters. Nevertheless electrochemical converters have not found widespread use, despite significant advantages over conventional energy systems. For example, compared to traditional energy systems, electrochemical converters such as fuel cells, are relatively efficient and do not produce pollutants. The large capital investment in conventional energy systems necessitates that all advantages of competing energy systems be realized for such systems to find increased use. Accordingly, electrochemical converter energy systems can benefit from additional development to maximize their advantages over traditional energy systems and increase the likelihood of their widespread use.
Accordingly, it is an object of the present invention to increase the efficiency of an energy system that employs an electrochemical converter.
It is yet another object of the invention to simplify energy systems that employ electrochemical converters.
It is yet a further object of the invention to provide a simplified and improved electrochemical converter energy system that extracts energy from waste heat generated by the electrochemical converter.
Although electrochemical converters have significant advantages over conventional energy systems, for example, they are relatively efficient and do not produce pollutants that have not yet found widespread use.